Follicular lymphoma presenting as a seminal vesicle mass: Diagnostic path from prostate MRI to ¹⁸F-FDG PET/CT

A 73-year-old man with biopsy-proven Gleason 3+3 prostate cancer presented with a new mass centered in the seminal vesicles with invasion of the base of the prostate on surveillance prostate MRI. Targeted biopsy showed atypical lymphoid proliferation, suspicious for lymphoma. The patient was referred to the nuclear medicine department for [18F]fluoro-D-glucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT). Multisite ¹⁸F-FDG-avid lymphadenopathy observed, as well as FDG uptake in the new mass. Core biopsy from dominant mesenteric mass revealed follicular lymphoma.